(a) Field of the Invention
The present invention relates to a terminal and a communication method thereof.
(b) Description of the Related Art
When a disaster or a calamity occurs, an important social infrastructure may be destroyed or damaged. Various communication facilities such as a wireless phone, a wired phone, and an Internet network are important social infrastructures, and when such a communication facility is destroyed or damaged, social congestion increases, and it may be difficult to secure society recovery.
Therefore, even in such a situation, a high reliability support that provides a method that can quickly restore or replace a communication facility is important.
Particularly, as a base station that performs a central function of communication of a mobile terminal is damaged or as a power line is destroyed, when the base station does not perform a function thereof, a service unavailable area may variously occur.
Therefore, it is necessary to provide a means that can provide a wireless communication service in a service unavailable area due to damage of a base station.
Nowadays, when a service unavailable area occurs, IEEE 802.16n, which is an international standardization conference, has suggested a method in which a multi-mode terminal performs a function of a relay mode or a base station as well as direct communication between terminals as a wireless communication replacement means. According to amendment working draft [1] of IEEE 8012.16n, when a mobile communication infrastructure may no longer operate a network or as an auxiliary replacement means according to a special mission, a multi-mode terminal can construct and operate a temporary network by a request of a superordinate base station or by converting a function thereof to a function of a relay station or a base station.
In this way, in order for the multi-mode terminal to perform a function of a relay station or a base station, it is necessary for a superordinate base station to select an optimal terminal to operate in a relay mode or a base station mode in lower multi-mode terminals. When candidate multi-mode terminals mount a satellite position-based system such as a GPS, the superordinate base station grasps a position of a multi-mode terminal using such a satellite position-based system and selects an optimal multi-mode terminal through the grasped position. However, when the multi-mode terminal does not mount a GPS, another method in which a superordinate base station grasps a position of the multi-mode terminal is necessary.